When Bronto began the development of our API, we built it on the current industry standard SOAP (Simple Object Access Protocol). Within the last year our newest services have begun offering REST (REpresentational State Transfer ) APIs. While there are no immediate plans to move our current SOAP APIs to REST, any future services will provide REST APIs.
So how do you know which API you need to use? If you are working with Product or Cart data, you will need to use REST calls. When you are working with Order data you will also want to use REST API calls, though you can add, update, or delete orders using SOAP functions. Everything else – contacts, lists, deliveries, messages, webforms, workflows, etc – is based on SOAP.